A well known problem associated with telescopic shock absorbers employing a damping piston reciprocating in a cylinder filled with a damping gas and/or fluid is the temperature dependent damping characteristics of the shock absorber.
The capacity of such shock absorbers to operate efficiently is limited in certain conditions of operation by their inability to dissipate heat resulting from fluid friction converting the undesirable kinetic energy of the vibrating mass into heat causing thermal overloading.
Generally an increase in the temperature of the damping fluid adversely affects the damping characteristics of the shock absorber. When a vehicle travels over rough terrain or on a racing circuit the rapid reciprocative axial movement of the damping piston causes the temperature of the damping fluid to rise rapidly and this can be exacerbated when the ambient temperature is relatively high and the vehicle is being operated at high speed.
U.S. Pat. No. 4,616,810 discloses a liquid cooled shock absorber employing a jacket which surrounds the damping chamber of the shock absorber and forms an annular outer chamber. Cooling fluid enters the annular chamber through a narrow, axially extending inlet passage open at the lower end of the annular chamber to allow circulation of the fluid around the remaining main portion of the annular chamber and thence through an outlet connection. The annular outer chamber is connected for fluid communication with the cooling system of the vehicle engine.
The shock absorber of this patent suffers from the disadvantages of lack of uniform distribution of the cooling liquid around the shock absorber cartridge and the lack of strength in the system in that the jacket and its shock absorber cartridge are subject to distortion due to the unequal cooling, and that being linked into the engine cooling system the temperatures therein required for efficient running of the vehicle engine are in the region of 80.degree. C. to 100.degree. C. In this situation with temperatures at the shock absorber in the vicinity of 100.degree. C. the strength of the shock absorber drops by approximately one third of its static strength.
It is an object of the present invention to stabilize the temperature of a shock absorber for consistent and efficient damping and to prevent the shock absorber reaching high temperatures over 100.degree. C. which can result in seal breakdown and high piston and bore wear distortion of the shock absorber cartridge. As the temperature of the shock absorber increases, the oil viscosity decreases whereby the damping effect is reduced and piston speeds increase resulting in excessive wear on the piston and its cylinder wall.
It is a further object of the present invention to provide a cooling system for a shock absorber incorporating a coolant casing around the shock absorber cartridge which greatly increases the strength of the shock absorber assembly and this is particularly advantageous in motor sport applications.
Yet another object of the present invention is the provision of a cooling system for a shock absorber which is independent of the vehicle engine cooling system wherein the engine coolant is too hot in most cases to maintain optimum operating temperatures for the shock absorbers and obviates any pipeline or shock absorber failure which could cause loss of engine coolant and serious engine damage.